130 



METEOROLOGY-FORECASTING 



New Guinea coast,'* iii(]i(/ates ilio oceurreiiec ui' an 

 elevated S-sliaped curve, below which is found simple 

 surface trapping or the usual trade wind surface in- 

 version. AVlule the existence of conditimis faAorabIc 

 to such effects off the coasts of Japan may be assumed, 

 on account of the lofty mountains, there are no 

 data available on this point. The only ijiformatiou on 



2000 



1600 



1200 



eoo 



-8 -6 -4 -2 



M-Mg 



Figure 22. M deficits calculated from soundings made 

 at Tateno, Honshu, 1928. 



ti'appiag in the Japanese area has been obtained from 

 a study of soundings made in 1938 at Tateno,'" on the 

 east coast of Honshu, some fifty miles from Tokyo. 

 The data, plotted in Figure 22, shows three cases of 

 an M inversion. The numerical quantities are given 

 in Table 3. 



T.'iBLE 3. Aerological soundings at Tateno, Honshu, in 

 1928, together with computed duct widths and the magnitude 

 of the M deficit. 



Elevation 

 of duet 

 Date top (ft) 



Elevation 

 of duct 

 base (ft) 



Duct Magnitude 

 widtli of M 



(ft) deficit 



May 1 

 August 23 

 September 29 



1,900 

 1,000 

 1,250 



1,300 

 650 

 950 



600 

 350 

 300 



-6 

 -5 



Note on Attu and the Aleutians-"'-^ 



Fixed echoes have been obtained at abnormally 

 long ranges (100 to 150 miles). The "Battle of the 

 Pips" was an illustration of pronounced superrefrac- 

 tion. The latter has been observed on at least four 



standard atmos- 

 (iO mm of 



(iccasions l>y operators of airborne radars returning 

 to Attu from missions over the Kuriles, when VHF 

 ladar beacons liave iclurned signals to planes at 5,000 

 ft and oOO to 350 miles, or about three times the 

 horizon line distance. Meteorological data on duct 

 conditions during the cycle of the Aleutian seasons 

 are needed (up to 1,000 ft). 



APPENDIX 



Stanoakd Atmospheke 



Definition. The National Advisory Committee on 

 Aeronautics [NACA] defines the 

 |iheic" as that wbiih cxliibits: 



1. A sea level pressure of 1.013 mb ( 

 lut'jcuiy = 29.92 in. of mercury). 



2. A sea level temperature of 15 C ( = 59 F) which 

 decreases at a rate of 6.5 C per km ( = 3A7 F per 1,000 

 ft) in the lower atmosphere; and in addition the 

 moisture content may be specified as follows: 



3. A relative humidity of 60 per cent, which corre- 

 sponds to a water vapor pressure of approximately 10 

 mb at sea le\el and to a rate of decrease in the lower 

 atmosphere of about 1 mb per 1.000 ft. 



Properties. The following table for the standard 

 atmosphere indicates the variation with height of (a) 

 temperature, (b) pressure, (c) water vapor pressure 

 for 60 per cent relative humidity, (d) a quantity con- 

 taining the index of refraction, /(, and (e) the modi- 

 lied rerracti\e index. J/. 



Water vajior 

 Temper- Pres- jwessure for 

 Altitude ature sure 60% RH 

 Meters Feet C F (mb) (mb) (n-l)xl06 M 



Radio METtooiiOLOGV Teums 



Inilf.r uf Hrfraction. This can be defined for any 

 particular medium as the ratio of the velocity of 

 electromagnetic waves in a vacuum to their velocity 

 in tlu' medium. The relationship indicating the 

 amount of bending or change in direction that occurs 

 as electromagnetic radiation crosses a boundary be- 

 tween two media with diH'erent refractive indices is 

 given by Suell's law : 



7ii cos ai = /i2 cos a2 

 in \\hi(h n^ is the refractive index of the first medium. 



